Speaking as someone who went through something very similar recently, I feel your pain. I wish you consolation in this difficult time. Losing a pet like that is awful. I still get torn up thinking about how cruelly Charlie was taken from us in what should have been the prime of his life. We've moved on and adopted two other cats who needed a loving home, but there's not a day that goes by that I don't think of Charlie (I still have his picture as my windows desktop at work and at home and likely won't change it anytime soon). I don't WANT to forget what a great companion he was.
Something to look into for the future - veterinary insurance. Yes, there really is such a thing and I have it on my cats now. The costs can simply get too high and the last thing I'd ever want is to be in a situation where it's up to money (or lack thereof) that forces me to have to see a family member (and I view my pets as nothing less) have to be put down.
Awful to hear. I'm with you. I hope things look up for you. Here's a link for you and anyone else so interested:
http://www.petsbest.com/ There's also VPI, which I think is offered through ASPCA, which is pretty good too.